Potential energy and dipole moment surfaces of HCO- for the search of H- in the interstellar medium.

Potential energy and permanent dipole moment surfaces of the electronic ground state of formyl negative ion HCO(-) are determined for a large number of geometries using the coupled-cluster theory with single and double and perturbative treatment of triple excitations ab initio method with a large basis set. The obtained data are used to construct interpolated surfaces, which are extended analytically to the region of large separations between CO and H(-) with the multipole expansion approach. We have calculated the energy of the lowest rovibrational levels of HCO(-) that should guide the spectroscopic characterization of HCO(-) in laboratory experiments. The study can also help to detect HCO(-) in the cold and dense regions of the interstellar medium where the anion could be formed through the association of abundant CO with still unobserved H(-).

On the electron-induced isotope fractionation in low temperature (32)O(2)/(36)O(2) ices--ozone as a case study.

The formation of six ozone isotopomers and isotopologues, (16)O(16)O(16)O, (18)O(18)O(18)O, (16)O(16)O(18)O, (18)O(18)O(16)O, (16)O(18)O(16)O, and (18)O(16)O(18)O, has been studied in electron-irradiated solid oxygen (16)O(2) and (18)O(2) (1 ∶ 1) ices at 11 K. Significant isotope effects were found to exist which involved enrichment of (18)O-bearing ozone molecules. The heavy (18)O(18)O(18)O species is formed with a factor of about six higher than the corresponding (16)O(16)O(16)O isotopologue. Likewise, the heavy (18)O(18)O(16)O species is formed with abundances of a factor of three higher than the lighter (16)O(16)O(18)O counterpart. No isotope effect was observed in the production of (16)O(18)O(16)O versus(18)O(16)O(18)O. Such studies on the formation of distinct ozone isotopomers and isotopologues involving non-thermal, non-equilibrium chemistry by irradiation of oxygen ices with high energy electrons, as present in the magnetosphere of the giant planets Jupiter and Saturn, may suggest that similar mechanisms may contribute to the (18)O enrichment on the icy satellites of Jupiter and Saturn such as Ganymede, Rhea, and Dione. In such a Solar System environment, energetic particles from the magnetospheres of the giant planets may induce non-equilibrium reactions of suprathermal and/or electronically excited atoms under conditions, which are quite distinct from isotopic enrichments found in classical, thermal gas phase reactions.